1. Field of the Invention
The present invention relates to controlling an engine and a belt-driven integrated starter generator (B-ISG) connected to the engine. Starting and stopping the engine is coordinated to occur when the B-ISG is capable of starting the engine.
2. Background Art
Integrated Starter-Generator (ISG) is an industry term for the electric machine used in Hybrid Electric Vehicles (HEVs). This term does not indicate the power level of the machine or the method of connection to the ICE, only that it is a single machine functioning both as a starter and a generator. Some publications use Combined Starter Alternator (CSA) or Combined Alternator Starter (CAS) instead of ISG, but all of these terms describe the same electric machine.
HEV systems and other non-HEV systems are typically designed to maximize fuel economy and reduce emissions. A basic fuel saving strategy, known as start-stop, is to shut the engine off when the vehicle is stopped, then to restart the engine when the driver intends to accelerate. An example of a more advanced and expensive strategy is to have the electric machine provide acceleration torque, which could allow a reduction in the size of the internal combustion engine. ISGs can be used to start the engine.
The method of connecting the ISG to the ICE is identified with a prefix. A Belt-ISG (B-ISG) connects to the engine through pulleys and a belt, while a Crank-ISG (C-ISG) connects directly to the crankshaft. The main benefit of B-ISG over C-ISG is lower cost due to the ability to package the system in an existing product without a major redesign. The main drawback is that the torque available at the engine is limited by belt slip at the pulley and by the belt strength.